package com.eascs.spider.yuqing.schdule.bloomfilter;

import java.io.Serializable;
import java.util.BitSet;

import org.springframework.stereotype.Component;

/**
 * 布隆去重器,
 * 启动调度中心会从redis读取或新建初始化，
 * 停止调度中心之前会将此实例持久化到redis
 * @author hzp
 *
 */
@Component
public class BloomFilter implements Serializable{
	
	private static final long serialVersionUID = -7917368899767252001L;
	
	private static final int DEFAULT_SIZE = 2 << 24;
    private static final int[] seeds = new int[] { 5, 7, 11, 13, 31, 37, 61 };
    private BitSet bits = new BitSet(DEFAULT_SIZE);
    private SimpleHash[] func = new SimpleHash[seeds.length];

    public BloomFilter() {
    	for (int i = 0; i < seeds.length; i++) {
            func[i] = new SimpleHash(DEFAULT_SIZE, seeds[i]);
        }
    }

    public void add(String value) {
        for (SimpleHash f : func) {
            bits.set(f.hash(value), true);
        }
    }

    public boolean contains(String value) {
        if (value == null) {
            return false;
        }
        boolean ret = true;
        for (SimpleHash f : func) {
            ret = ret && bits.get(f.hash(value));
        }
        return ret;
    }

    // 内部类，simpleHash
    public static class SimpleHash implements Serializable{
     
		private static final long serialVersionUID = -3585350675218394454L;
		private int cap;
        private int seed;

        public SimpleHash(int cap, int seed) {
            this.cap = cap;
            this.seed = seed;
        }

        public int hash(String value) {
            int result = 0;
            int len = value.length();
            for (int i = 0; i < len; i++) {
                result = seed * result + value.charAt(i);
            }
            return (cap - 1) & result;
        }
    }
}
